not much differance mostly cam,timing,comp ratio not enuff to talk about
stock rebuild?aftermarketcam? milled heads?
how does it run?I hope good,I hate it when you get a motor rebuilt with nothing but probs.
chiltons manual will tell all you need to know about a stock motor.

i took it to a real rural macine shop and they did an excellent job. i dropped the truck off and they did all of the rest for $1760 installed. a it had some busted rings and bad blow-by. they replaced pistons, cams,valves, water pump, oil pump, plugs, all new gaskets, turned the crank, rebuilt and reground heads, new timing chain and new belts. they also bored the block and replaced every fastener in it. there is more but i forgot. it runs better than it ever has before and hasn't given any problems.

The 351W H.O. has about 70 more HP than the plain 351W. The Broncos were never meant to go fast, as you can see from the low peak RPM's and a weight of about 5600 pounds. Still, a fresh motor will glue you to the seat when you punch it!!

I think that a fresh motor that is professionally tuned will perform well.
if you have a motor rebuilt you get things changed and that is why hghby73 asked about the machine work.
not very many vechicles are made to go fast that's why we have tools and brains,to make them go fast.i've seen a fullsize bronco do 13's in the 1/4 mile
that's pretty quick by any standards.
so if you are happy with stock then stay with it but just cause you get it rebuilt by someone doesn't mean it'll perform well.do you know what cam you have?how much was took off your heads?all of this pertains to your horse power.
did you curve your distributer to match your cam profile?did you replace the distributer?have you took out your plugs and checked them since the rebuild?are they indexed?just because it sounds good or what you may think runs good doesn't mean you don't need to check.a lean condition will melt a piston.did you get your motor bored?file fitted rings?these are some of the things that make all the diff in life and death.
call me what you like but i am right

I have all of those stats written down but basically the motor is stock. the motor was bored .030 and it has file fitted rings. i checked the sparkplugs last week and they were fine and looked great. i dont have the time to do all of the other things, But all of the setting were set to stock from the macine shop. basically all of the emisson controls are gone but none of them worked. i checked several times. the next thing i need to do is get new headers and an intake and exahust system. i don't race so im not trying squeeze every hp of the motor but it is nice to have a general idea. it comes down to money. stock is cheap.

I'm new and just happen to be looking thru the posts is the 351 EFI or carb if its EFI having the emission off can cause the motor to run lean. but yah the Bronco's neer had a real strong runner from the Factory and the Hp changed after 86 i think, the made the motor more earth freindly and with less Hp

FYI, the 351W H.O. was only offered from 1984-1986, and it had a [crappy] 4-bbl. Holley carb. The 1987 and up 351W were not H.O., but were MPFI and had about the same HP as the H.O., except for the Lightning motors that had a bit more. Most people that think the 302 is a dog don't know that it has nearly the same HP as the 351W, and can be made to run better with slight or mild mods like for the 351W...